Re: [CAD_CAM_EDM_DRO] cooling motors simultaneously killing bacteria

Hi John,

I did quite a bit of work on Legionnaires Disease in my 'previous' life. The
bug which causes the disease is one of the commonest in our environment, it
is found in almost all water supplies, streams, rivers etc. and is very hard
to kill. However, to be dangerous to us there are four factors which need to
be present.
1. It needs to be there in 'sufficient quantity' - no one really knows what
this means but it is generally assumed that, from the bug getting into a
system, it will take at least a fortnight for it to multiply enough to cause
problems.
2. It needs a suitable environment to grow - it needs warmth, dark and the
presence of amoeba in which it spends part of its development cycle. These
usually live in the slime covering the surfaces of dirty water tanks, pipes
etc. The ideal situation for the growth of these bugs is the air scrubber
section of older air conditioning systems or 'fixed' washing systems like
car washes.
3. There needs to be an 'aerosol' - droplets above a certain size will not
penetrate far enough into the lungs to allow the infection to get a hold. A
fine mist is its ideal transport mechanism. This may, of course, be produced
by rebound of a jet of fluid from a worpiece, especially if it is warm.
4. The person has to be susceptible to this infection - it doesn't usually
affect fit and healthy people but tends to affect the elderly and smokers
whose lungs are already weakened.
Many cutting oils are indeed a good breeding ground for bugs such as
Legionnaires and the fact that the cooling systems are seldom cleaned out
and are usually situated in a 'comfortable' workshop environment compound
the problem. These are only two types of disinfectant which are effective at
eradicating these bugs - Chlorine based ones such as bleach (the most
effective) and certain Phenols which are often added to cutting oils purely
for this purpose.
Because the bugs live in slimes, they are difficult to get at simply with
liquid disinfectsants and so physical scrubbing is really recommended but,
if you want to be reasonably certain of keeping your system free of
infection you could a). use only cutting oils containing an effective
disinfectant, b) physically clean out your system frequently, c) empty the
tank every two to four weeks, refill it with a bleach solution or a
phenol-based disinfectant and pump this through the lines, allowing it to
stand for an hour or so to work thoroughly before emptying it out again and
d) use a flood coolant system rather than mist.

Ian
--
Ian W. Wright
Sheffield UK
www.iw63.freeserve.co.uk

----- Original Message -----
From: <e.heritage@...>



> Someone a few miles from us got Legionaires recently and it reminded me of
> the mist or flood thread. There was a worry Legionaires might take up
> residence in mist systems